1. Field of the Invention
The present invention relates generally to vehicle steering, and in particular to a hydraulic safety interrupter for automatic steering (“autosteer”) systems, which can use sensors including Global Navigation Satellite System (GNSS), and other guidance and navigation receivers and equipment.
2. Description of the Related Art
A. GNSS-Based Vehicle Guidance Background
The use of sensors for automating vehicle guidance and machine control has significantly advanced these fields and enabled a number of applications, including many in agriculture, transportation and other industries. For example and without limitation, GNSSs are commonly used for guidance, navigation and machine control. GNSSs include the Global Positioning System (GPS) and other satellite-based systems. Various GNSS receivers are available for aviation, marine and terrestrial vehicles. The GNSS information provided by such receivers can be processed and used for navigation. In more sophisticated systems, vehicle guidance can be automatically controlled using such information. For example, a predetermined travel or flight path can be programmed into an on-board computer. The vehicle guidance system can automatically maintain appropriate course parameters, such as course, heading, speed, altitude, end-of-row U-turns, etc. Control system, feedback theory, and signal filtering techniques can be used to interactively anticipate (with higher order systems) and compensate for course deviations and navigation errors. Such sophisticated autopilot and automatic steering systems tend to involve powerful computers and complex flight and steering controls integrated with manual controls.
Accurate vehicle guidance and equipment control are important objectives in agricultural operations generally and agricultural equipment specifically. For example, cultivating, tilling, planting, spraying, fertilizing, harvesting and other farming operations typically involve specialized equipment and materials, which are operated and applied by making multiple passes over cultivated fields. Ideally, the equipment is guided through accurately-spaced passes or swaths, the spacing of which is determined by the swath width of the equipment.
GNSS technology advanced the field of agricultural guidance by enabling reliable, accurate systems which are relatively easy to use. GNSS guidance systems are adapted for displaying directional guidance information to assist operators with manually steering the vehicles. For example, the Outback steering guidance product line was developed primarily for agricultural applications. Current GNSS-based products include the Outback S3, the eDrive TC and the eDrive X™ which are available from Outback Guidance (www.outbackguidance.com) and are manufactured by AgJunction, Inc. (www.agjunction.com) of Hiawatha, Kans. These products are covered by U.S. Pat. No. 6,539,303 and U.S. Pat. No. 6,711,501, which are incorporated herein by reference. They include on-board computers which can be programmed for steering vehicles through various straight-line and curved (“contour”) patterns. An advantage of this system is its ability to retain field-specific cultivating, planting, spraying, fertilizing, harvesting and other patterns in memory. This feature enables operators to accurately retrace such patterns. Another advantage relates to the ability to interrupt operations for subsequent resumption by referring to system-generated logs of previously treated areas.
The OUTBACK S™ GNSS guidance system provides the equipment operators with real-time visual indications of heading error with a steering guide display and crosstrack error with a current position display. They respectively provide steering correction information and an indication of the equipment position relative to a predetermined course. Operators can accurately drive patterns in various weather and light conditions, including nighttime, by concentrating primarily on such visual displays. Significant improvements in steering accuracy and complete field coverage are possible with this system.
Another type of GNSS vehicle guidance equipment automatically steers the vehicle along all or part of its travel path and can also control an agricultural procedure or operation, such as spraying, planting, tilling, harvesting, etc. Examples of such equipment are shown in U.S. Pat. No. 7,142,956, which is incorporated herein by reference. U.S. Pat. No. 7,437,230 shows satellite-based vehicle guidance control in straight and contour modes, and is also incorporated herein by reference.
GNSS guidance systems and equipment are distinguished by their vehicle path configuration capabilities. Initially, straight-line AB (i.e., between points A and B) guidance consists of multiple, parallel straight lines, which are separated by the swath widths of the vehicles. Straight line AB guidance is ideally suited for rectangular fields and continuously-repeating, parallel swathing.
Non-rectangular and terraced fields typically require curvilinear vehicle paths that follow the field perimeters and the terraced elevation contours. Contour guidance systems and methods were developed to accommodate such field conditions using GNSS coordinates to define curvilinear vehicle paths. See, for example, Korver U.S. Pat. No. 5,928,309. GNSS positions can be logged on-the-fly at intervals of, for example, 0.20 seconds. Contour guidance can be accomplished by computer-generating each subsequent pass from the GNSS-defined previous pass and a user-entered swath width.
Another type of GNSS contour guidance equipment outputs guidance signals relative to the edges of all previously logged swaths. Such logged swaths typically correspond to field areas where operations, e.g. spraying, have already been carried out. See, for example, U.S. Pat. No. 6,539,303 and U.S. Pat. No. 6,711,501, which are assigned to a common assignee herewith and are incorporated herein by reference.
Automatic steering accommodates “hands-off” operation, taking into account vehicle operating parameters, such as turning radii, speeds, swath widths, etc. Appropriate machine control functions, such as implement steering and spray boom control, can also be automated.
B. Manual-Automatic Steering Interface
Although agricultural operations have utilized robotic equipment without human operators on-board, standard practice is to provide an operator with the ability to override the automatic steering system. For example, some automatic steering systems will disengage when operator input, e.g., via steering wheel, is sensed. On-board computers can detect such manual turning inputs and issue appropriate output commands for disengaging auto-steering functions. GNSS-guided automatic steering can be accomplished with hydraulic valve blocks retrofit on existing vehicles, or installed as original equipment in new vehicles. GNSS receivers provide positioning and navigation data, which can be processed by on-board microprocessors for steering and other vehicle control functions. An advantage of the present invention is to provide a hydraulic steering interrupter which is manually-activated and is independent of the automated, computerized steering controls. Heretofore there has not been available a hydraulic steering interrupter with the advantages and features of the present invention.